A system for transmitting and displaying image information, such as an original image, imaged by a camera, once encodes/compresses the original image, and transmits it. After this, the system displays an image (decoded image) which has been obtained by decoding the image. Because the image information generally includes a large quantity of information, it is necessary to limit a transmission bandwidth in a transmission as a network. In this image transmission system, image recognition may sometimes be required, instead of or in addition to the displaying. For example, a monitoring camera finds any suspicious persons, while an onboard camera obtains the space between vehicles recognizes traffic signs, or performs image recognition in order to avoid collision with pedestrians, other vehicles, and any other obstructions.
Japanese Unexamined Patent Application Publication No. 2008-22404 discloses an image encoding apparatus. This apparatus includes a feature amount extracting section on the front stage of image recognition, obtains a flatness level (activity) of an image using a feature amount calculating section, and improves the image quality by determining parameters regarding the deblocking filter included in an image encoding process.
Japanese Unexamined Patent Application Publication No. 2013-239995 discloses a method for realizing a high recognition rate in an onboard camera system for driving assistance for vehicles. In this system, a video transmission device encodes and transmits a video image, and image recognition is performed using a video image decoded by a video reception device. The video reception device transmits encoding control information (such as an image size of a moving image format, a color format, a frame rate, a bit depth) to an encoder control section of the video transmission device, in accordance with a traveling state of the vehicle and the driving assistance application (such as a lane deviation warning, collision prevention, or displaying of the rear moving image). The transmission side changes an encoding mode based on the encoding control information, and generates a moving image stream. For example, when a video signal is output to an external display device, a deblocking filter function is ON. On the contrary, the deblocking filter function is OFF, when it is used for an image recognition process. This prevents a decrease in the recognition rate, because edge information deteriorates (the paragraph “0048” of the same literature). In addition, the recognition rate can further be increased (the paragraph “0044” of the same literature). For this increase, a noticed area is determined through rough search as preprocessing of the image recognition process, this information is transmitted to the side of an encoding unit, and a quantization step width of the noticed area is controlled to be small by an encoding process of the encoding unit side.